This invention relates to manhole cover supports for emplacing over and raising the grade of an existing manhole cover-receiving structure in a roadway, particularly to such supports that can be used to accommodate a group of manhole covers of a standard size and shape where the frames thereunder diverge somewhat as to the size of the otherwise geometrically similar covers that they can take.
For simplicity the term "existing manhole cover-receiving structure" is used here to refer to the existing, i.e., fixed in-place frame or other seating receptacle for a removable cover or grating that covers an access hole (i.e., hand hole, tool hole, manhole, catch basin or the like). The term "manhole cover" is used to refer to the removable cover or grating over the access hole. The resulting assembly of a receiving structure and a manhole cover ordinarily is intended to bear vehicular traffic. The term "manhole cover support" or simply "cover support" here means a structure that fits over the existing manhole cover-receiving structure, raises its grade, and thereby accommodates a cover or grating at its new elevated grade. The access hole covered is a utility enclosure serving, e.g., an electric, gas, water, sewer or storm drainage system.
The preponderance of manholes are circular (in street plan), have circular covers and have existing cover-receiving structures such as frames that are circular with circular cover keepers (also sometimes called "collars" or "riser rings"). Accordingly, much of this specification is directed to round manhole cover supports that have ring-like annular elements which are to interact with an existing round manhole cover-receiving structure. However, it should be understood that this invention can be utilized in connection with other shapes of cover support, e.g. rectangular, square, triangular, hexagonal and so on, and further that the instant cover support which is to be fitted to the usual circular hole of a frame can be adapted to take a round cover or one other than round, e.g. hexagonal, and even still further, this cover support need not have an outer periphery at pavement level that is round--that periphery can be, for example, square or octagonal.
Ordinarily a cover support finds its use when a roadway such as a street or highway is resurfaced with an added layer of paving material, typically asphalt concrete or sheet asphalt, to establish a higher grade. A principal use for the instant cover support is expected to be in a municipality where a group of manhole installations of somewhat varying diameters are likely to be encountered in the resurfacing. Thus, adjoining or the same subdivisions, boroughs, wards or districts may have existing manhole cover frames for accommodating a group of covers that are nominally of several fairly close sizes, say 221/2 to 24 inches in diameter. When resurfacing in such an area, it may be decided to standardize on a single size 23-, 24- or 25-inch diameter cover for this group to reduce the inventory of covers, purchase them in larger lots, avoid potentially costly custom-built equipment or short manufacturing runs by a single or a limited few manufacturers, and certainly to eliminate the digging out, raising and resetting of the existing frames or other cover-receiving structures simply to accommodate their original variously-sized manhole covers. It then can be especially advantageous to mount the inventive cover supports atop these existing manhole cover frames for the standardization purpose.
Heretofore the typical installation of new manhole cover supports has seemingly been circumscribed by and restricted to the reuse of the old cover. The possible benefits of standardizing on a new cover size (and possibly shape) in place of a group of geometrically similar covers that vary a little in size from one to another or from one subgroup to another, then designing a new cover support expressly for the new standardized covers appears to have gone unrecognized; it does not seem to have been addressed at all by the art.
Like the related manhole cover supports whose fixed-sized top flanges are borne on the upper rim of a manhole frame or other existing manhole-receiving structure, the instant cover support offers the economies efficiency and simplicity of such standardization practice. However, elevations of the peripheral flange of the instant cover support well above the upper rim of a manhole frame or other existing manhole cover-receiving structure can be established with less bulk and greater simplicity than when using such related cover supports. Furthermore, some embodiments of the instant invention can be adjusted as to height comparatively rapidly and effectively by including an elevation selection feature that is not present in such related fixed-size top flange-type cover supports.
Frequently, also, the roadway where the cover support is to be installed has a distinct crown. If the manhole cover can be seated at an incline that approaches the incline toward the crown, or at least compensates for a substantial portion of such incline, the repaving will be smoother. The instant cover support lends itself to the providing of such seating (even if the seat needs to have a plurality of inclines for a cover that is not flat, as for one that is near the intersection of two high-crowned streets). This is because the top flange in the instant invention is one-piece (either assembled as with bolts from a plurality of pieces or one solid piece).
Prior art on manhole cover supports and manhole cover frames can be found in U.S. Pat. Nos. 4,963,053, 4,872,780, 4,867,601, 4,281,944, 4,236,358, 4,203,686, 3,968,600, 3,773,428, 4,225,266, 4,302,129, 4,097,171, 4,302,126, 3,891,337 and 1,987,502. The first eight of these are for inventions of the applicant.
Axle loads up to 18,182 kg. must be resisted by many of these cover supports as well as serious impact loads from vehicles and snow plows, a variety of temperature effects, steam leaks, spillage, etc., without permitting a hazardous dislocation of the cover support or its cover. Often it is desirable also to cushion the cover for resisting wear or reducing noise, and/or to seal the cover and its cover support against a substantial and possibly overloading infiltration of surface water, e.g., storm drainage that otherwise would enter a sanitary sewer system at various manhole locations.
The instant cover support can be made especially highly resistant to displacement and dislodgement in service. Thus, while it preferably incorporates structural or mechanical hold-down (anchoring) means to the existing manhole cover-receiving structure, such anchoring extensions being integral with the cover support or easily attached to it, the instant cover support also can be constructed to do a good job of holding in (being retained in the existing manhole cover-receiving structure, such as a frame, while in service) by friction alone.